We have synthesized the activated form of the carcinogen benzo(a)pyrene (BaP), (plus or minus) 7 Beta, 8 alpha-dihydroxy-9 alpha, 10 alpha-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene ((plus or minus) anti-BaP diol epoxide), and determined through fluorescence, absorbance and circular dichroism spectroscopy and high resolution mass spectrometry that the hydrocarbon reacts to form a pair of diastereomers with the exocyclic amino groups of deoxyguanosine, deoxyadenosine and probably deoxycytidine in DNA. This reaction is stereoselective for guanine in double stranded DNA but not with single stranded polydeoxynucleotides or with monodeoxynucleotides. Physical interactions between the hydrocarbons and DNA prior to alkylation may play a role in asymmetric covalent binding. The goal of this proposal is to understand the asymmetric interactions between this potent carcinogen and DNA. Specifically, we will investigate 1) the role of intercalation in this binding process by spectral analysis of physical complexes and the kinetics of their binding process by spectral analysis of physical complexes and the kinetics of their formation; 2) possible sequence specific covalent binding by use of DNA sequencing techniques; 3) mutagenesis mechanisms by replicating hydrocarbon modified DNA in vitro and sequence analysis of the newly synthesized strand; and 4) the relevance of DNA covalent adducts to the biological properties of BaP by analyzing in vivo adducts from target (skin) and non-target (liver) tissues. In the latter case, comparing relative repair rates, in addition to adduct analysis, may also provide information on the biological relevance of BaP-DNA alkylation products.